Low-mass planets in nearly inviscid disks: Numerical treatment

Embedded planets disturb the density structure of the ambient disk and gravitational back-reaction will induce possibly a change in the planet's orbital elements. The accurate determination of the forces acting on the planet requires careful numerical analysis. Recently, the validity of the often used fast orbital advection algorithm (FARGO) has been put into question, and special numerical resolution and stability requirements have been suggested. In this paper we study the process of planet-disk interaction for small mass planets of a few Earth masses, and reanalyze the numerical requirements to obtain converged and stable results. One focus lies on the applicability of the FARGO-algorithm. Additionally, we study the difference of two and three-dimensional simulations, compare global with local setups, as well as isothermal and adiabatic conditions. We study the influence of the planet on the disk through two- and three-dimensional hydrodynamical simulations. To strengthen our conclusions we perform a detailed numerical comparison where several upwind and Riemann-solver based codes are used with and without the FARGO-algorithm. With respect to the wake structure and the torque density acting on the planet we demonstrate that the FARGO-algorithm yields correct results, and that at a fraction of the regular cpu-time. We find that the resolution requirements for achieving convergent results in unshocked regions are rather modest and depend on the pressure scale height of the disk. By comparing the torque densities of 2D and 3D simulations we show that a suitable vertical averaging procedure for the force gives an excellent agreement between the two. We show that isothermal and adiabatic runs can differ considerably, even for adiabatic indices very close to unity.Comment: accepted by Astronomy & Astrophysic

Intestinal helminths of red foxes (Vulpes vulpes) in north-west Italy

SummaryA total of 180 foxes (Vulpes vulpes) from an area scarcely investigated of north-west Italy, were examined for intestinal helminths using sedimentation and counting technique (SCT). Faecal samples were submitted to centrifugation with 50 % zinc sulphate used as flotation solution.No fox was found completely negative for intestinal helminths. The most frequently identified nematodes were Uncinaria stenocephala (70.0 %), Molineus legerae (27.2 %), Toxocara canis (26.7 %), Toxascaris leonina (25.6 %), Trichuris vulpis (21.1 %), Aonchotheca putorii (8.9 %), Pterygodermatites affinis (5.6 %). Genus Mesocestoides (81.7 %), family Dilepididae (29.4 %) and Taenia spp. (8.3 %) were the most prevalent cestodes. All foxes were negative for E. multilocularis and E. granulosus. In two foxes trematodes belonging to the family Plagiorchidae were found.The study highlighted that foxes are hosts of intestinal helminths of veterinary and medical importance which may be transmitted to dogs and humans

Evaluation of a Rapid Device for Serological Diagnosis of Leishmania infantum Infection in Dogs as an Alternative to Immunofluorescence Assay and Western Blotting

In this study, we compared a rapid immunochromatographic test (Speed Leish K; BVT Groupe Virbac, La Seyne sur Mer, France) with an indirect immunofluorescence assay (IFAT) and Western blotting (WB) for the detection of Leishmania infantum antibodies in dogs. A total of 250 serum samples were collected from 125 L. infantum-positive and 125 L. infantum-negative dogs. Among the positive samples, 81 were strongly positive at low IFAT dilutions, while 44 were low-reactivity sera (IFAT titers, 1:40 to 1:80). The sensitivity and specificity of the Speed Leish K were 96.3% and 100%, respectively, compared with those of the IFAT. When IFAT low-reactivity sera (titers, 1:40 or 1:80) were tested with the Speed Leish K, using WB results as a reference, the sensitivities were 93.75% for sera with a 1:80 titer and 73.33% for sera with a 1:40 titer, and the specificity was 100%. The Speed Leish K is easy to use and performs well, so it can be considered a quick and reliable tool for the diagnosis of L. infantum infection in dogs

Calodium hepaticum (Nematoda: Capillaridae) in a red fox (Vulpes vulpes) in Italy with scanning electron microscopy of the eggs

Calodium hepaticum (Bancroft, 1893) Moravec, 1982 (syn. Capillaria hepatica) is a cosmopolitan capillariid nematode, infecting mainly rodents and occasionally other mammals, including humans. Reports of C. hepaticum in canids are rare and the present one is, to the best of our knowledge, the first reported case in a red fox (Vulpes vulpes Linnaeus) in Italy. Scanning electron microscopy (SEM) examination of the eggs of C. hepaticum allowed a precise description of the egg morphology, which is one of the most relevant specific characteristics of capillariid nematodes. The egg shell showed a fibrous beam-like network which differs from that of the eggs of closely related trichinelloid species. This characteristic can be useful especially in case of spurious infection, when misdiagnosis among different trichinelloids species can occur

3D MHD modeling of twisted coronal loops

We perform MHD modeling of a single bright coronal loop to include the interaction with a non-uniform magnetic field. The field is stressed by random footpoint rotation in the central region and its energy is dissipated into heating by growing currents through anomalous magnetic diffusivity that switches on in the corona above a current density threshold. We model an entire single magnetic flux tube, in the solar atmosphere extending from the high-beta chromosphere to the low-betacorona through the steep transition region. The magnetic field expands from the chromosphere to the corona. The maximum resolution is ~30 km. We obtain an overall evolution typical of loop models and realistic loop emission in the EUV and X-ray bands. The plasma confined in the fluxtube is heated to active region temperatures (~3 MK) after ~2/3 hr. Upflows from the chromosphere up to ~100 km/s fill the core of the fluxtube to densities above 109 cm-3. More heating is released in the low corona than the high corona and is finely structured both in space and time.Publisher PDFPeer reviewe

Unusual localization of pennella sp. In swordfish (xiphias gladius) hearts

The genus Pennella comprises hematophagous parasites of marine aquatic species, including cephalopods, marine mammals, and pelagic fish. Nine species have been officially included in the genus Pennella plus another six species inquirendae. They are most often found in the host’s musculature, without penetrating internal organs. For the present study, 83 hearts from swordfish (Xiphias gladius) caught in the Mediterranean Sea were sampled and immediately fixed in formalin for histopathological analysis. In total, 10 (12.05%) hearts were found to be parasitized by copepods of the genus Pennella. Macroscopically, there was mild-to-severe fibrinous pericarditis with atrial wall thickening and multiple parasitic nodules. Histologically, the parasitic nodules were surrounded by an inflammatory-necrotizing reaction. Parasitic infestation by Pennella spp. is common in pelagic fish and in swordfish, in particular. Here, however, we report atypical cardiac localization. A future area of focus is the evaluation of cardiac Pennella spp. infestation by histopathology and genetic identification of the parasites

Morphology of radio relics I: What causes the substructure of synchrotron emission?

High-resolution radio observations of cluster radio relics often show complex spatial and spectral features. However, it is not clear what these features reveal about the underlying magnetic field properties. We performed three-dimensional magneto-hydrodynamical simulations of merger shock waves propagating through a magnetised, turbulent intracluster medium. Our model includes the diffusive shock acceleration of cosmic-ray electrons, their spatial advection and energy losses at run-time. With this set-up we can investigate the relation between radio substructure and pre-shock plasma conditions in the host cluster. We find that upstream turbulence plays a major role in shaping the properties of radio relics produced downstream. Within the assumption of diffusive shock acceleration, we can reproduce the observed discrepancy between the X-ray derived Mach number of shocks, and the Mach number inferred from radio spectra. Our simulated spectral index maps and profiles across the radio relic also suggest that the standard deviation of the upstream magnetic field must be relatively small ($\sigma_B\leq 1 \, \mu$G) in order to reproduce observations and therefore, radio relics can potentially constrain the distribution of magnetic fields in galaxy clusters outskirts.Comment: Accepted for publication in MNRAS, 22 pages, 25 figure